1. Field of the Invention
The present invention relates to a working vehicle having an engine cooling fan and a muffler.
2. Description of Related Art
A conventional working vehicle having an engine cooling fan and a muffler is known to have a structure as described in (1) or (2) below. (1) A muffler main body and an exhaust pipe are provided in an upper rear portion of an engine immediately before an exhaust grill. A radiator cooling fan provided on the front side of the engine cools the muffler main body and the exhaust pipe (refer to Related Art 1). (2) A muffler main body is provided in an upper portion of an engine on a downstream side in an air blowing direction of a radiator cooling fan. An exhaust pipe extending from the muffler main body is composed of an upstream exhaust pipe portion on the muffler main body side and a downstream exhaust pipe portion that discharges exhaust outside and is fitted externally to the upstream exhaust, pipe portion with a gap for an ejector. Cooling air is forced into the fitted portion of the upstream exhaust pipe portion and the downstream exhaust pipe portion by velocity pressure of an engine cooling fan so as to reduce exhaust temperature (refer to Related Art 2).
[Related Art 1] Japanese Patent Laid-Open Publication No. H5-16679 (paragraph [0007]; FIGS. 1 and 2)
[Related Art 2] Japanese Patent Laid-Open Publication No. H7-277012 (paragraphs [0008] and [0010]; FIGS. 2 and 4)
In the structure disclosed in Related Art 1, the muffler main body is provided at a relatively high position in the upper rear portion of the engine and in the air path of the cooling air from the cooling fan. Furthermore, the exhaust pipe directing exhaust to outside from the muffler main body is also provided in the air path of the cooling air and is directed to the exhaust grill. Thus, the structure is effective to prevent a temperature increase under a hood due to a temperature increase of the muffler and to reduce the exhaust temperature from the muffler. Recently, however, a muffler main body having a catalyst thereinside is employed as a measure for exhaust gas to prevent environmental contamination. In this case, it is necessary to maintain the inside of the muffler main body at a relatively high temperature to effectively exhibit the catalytic function. If the cooling air does not sufficiently blow onto the muffler main body to maintain the temperature inside the muffler main body, the exhaust temperature from the exhaust pipe may be too high.
As disclosed in Related Art 2, the exhaust pipe extending from the muffler main body is elongated, and the cooling air is forced into the gap at the fitted portion of the upstream exhaust pipe portion and the downstream exhaust pipe portion by the velocity pressure of the cooling fan. The cooling air and the long exhaust pipe are thus used to reduce the exhaust temperature. It is difficult, however, to employ the structure in a small working device since there is not sufficient space to accommodate the long exhaust pipe. Furthermore, the muffler main body, which needs to be maintained at a high temperature, is positioned in the air path of the cooling fan in order to position the fitted portion in the air path of the cooling fan. A measure is also required to prevent excessive cooling due to the cooling air directly affecting the muffler main body, thus possibly leading to a further complex structure and an increase in the number of components.